It's been 1 month and no answer so based on the fact that removing the cdemu daemon remedied the problem, I'm going to presume it was a vhba issue and most likely already fixed upstream (current version works fine on kernel 3.0.0 or prior). Marking as Invalid bug for xorg-server.
** Changed in: xorg-server (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/768893 Title: System crashes when cdemu is present To manage notifications about this bug go to: https://bugs.launchpad.net/cdemu/+bug/768893/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs